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Calculating distortion summaries for circuit distortion analysis

a circuit and distortion analysis technology, applied in the field of circuit analysis, can solve the problems of inability to separate, generally requires high-order device derivatives, and the application of volterra series has typically been limited to simple models and simple circuits

Active Publication Date: 2009-08-04
CADENCE DESIGN SYST INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The present invention provides improved methods and systems for analyzing distortion in circuits, particularly analog and RF circuits. The methods involve determining the operating point of the circuit, identifying the nonlinear and linear offset values, and evaluating the nonlinear offset at different frequencies to determine the contributions to distortion. These methods can be used to improve the design and performance of circuits, as well as diagnose and troubleshoot existing circuits. The invention also includes an apparatus for carrying out the methods and a computer-readable medium that stores the computer program for carrying out the methods.

Problems solved by technology

While in general such a separation is not possible for most nonlinear effects because of cross terms between devices, insights on distortion dependency on nonlinearity in a single device can still be obtained by conducting some heuristic analysis.
A drawback of the Volterra method is that it generally requires high order device derivatives, which usually are not provided by device models used in real design simulations.
As a result, the application of Volterra series has typically been limited to simple models and simple circuits.
In general, current methods do not adequately model circuit distortion in terms of contributions from separate device elements.

Method used

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  • Calculating distortion summaries for circuit distortion analysis
  • Calculating distortion summaries for circuit distortion analysis
  • Calculating distortion summaries for circuit distortion analysis

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Embodiment Construction

1. Introduction

[0021]FIG. 1 shows a system 102 (e.g., a circuit model) that receives an RF input 104 with an input frequency ωRF and produces an output 106 where the input frequency has been modulated by the system (e.g., shifted by a multiple of the LO (Local Oscillator) frequency ωLO. Under non-ideal conditions, the output 106 includes distortions due to the nonlinear effects in the system 102. As described below, the present invention enables quantitative characterizations of how component devices contribute to distortion in the output signal 106. Specific embodiments include calculations for compression distortion and second-order intermodulation products (IM2). This application is related to CALCULATING INTERMODULATION PRODUCTS AND INTERCEPT POINTS FOR CIRCUIT DISTORTION ANALYSIS (application Ser. No. 11 / 303,049, filed Dec. 14, 2005), which is incorporated herein by reference in its entirety.

2. Compression Distortion Summary

[0022]The circuit 102 in FIG. 1 has a periodic time-de...

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Abstract

Methods for analyzing circuit distortion based on contributions from separate circuit elements are presented. Local approximations that do not require high-order derivatives of device models are developed near an operating point for calculating distortion summaries including compression summaries and second-order intermodulation (IM2) distortion summaries.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims the benefit of U.S. Provisional Application No. 60 / 750,706, filed Dec. 14, 2005, and incorporated herein by reference in its entirety.BACKGROUND OF THE INVENTION[0002]The present invention relates to the analysis of circuits generally and more particularly to the distortion analysis of analog and RF (Radio Frequency) circuits by calculating distortion contributions of individual circuit elements.[0003]Circuit linearity is a critical specification in analog and RF designs. Intermodulation product and compression are two commonly adopted measures for distortion [6, 11]. As a result, a general methodology for analyzing effects of individual components on circuit distortion and for identifying the major sources of nonlinearity is of practical importance in complex designs. From the designer point of view, it is desirable to separate total distortion into contributions of different elements. While in general such a sepa...

Claims

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Application Information

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Patent Type & Authority Patents(United States)
IPC IPC(8): G06F17/50G06F9/45
CPCG06F17/5063G06F17/5036G06F30/36G06F30/367
Inventor RAO, FANGYIFENG, DAN
Owner CADENCE DESIGN SYST INC
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